The Voynich Manuscript has been carbon dated to somewhere between 1404 and 1438:

Using radiocarbon dating, a team led by Greg Hodgins in the UA’s department of physics has found the manuscript’s parchment pages date back to the early 15th century, making the book a century older than scholars had previously thought.

This rules out Leonardo da Vinci as the author, which was my personal favorite theory. da Vinci was born in 1452. It also rules out John Dee and Edward Kelly, who lived in the 16th century. It also of course rules out the possibility that Voynich forged the manuscript.

I give examples to show that the code used in the Voynich Manuscript is probably a series of Italian word anagrams written in a fancy embellished script. This code, that has been confusing scholars for nearly a century, is therefore not as complicated as it first appears. [...]

I used an Internet site, ‘Italian Anagram Dictionary,’ to help me unscramble the words and translate the anagrams into English. The book ‘The Botanical Gardens of Padua 1545-1995’(iv) helped identify some of the common names used for plants in Italy in the 16th century. You can judge from the examples given below, whether this Anagram Code has been successful deciphering this limited selection from the Voynich Manuscript. I hope some of you who read medieval Italian will help decipher more of the manuscript so we can finally learn the mysteries, if any, that this manuscript is hiding.